The basic functions of circuit breakers are to provide electrical system protection and coordination whenever abnormalities occur in any part of the system. The circuit breakers provide a mechanism for interrupting the electrical circuit upon the occurrence of an overload or fault condition.
Circuit breakers are often mounted in board arrangements or cells such as drawout switchgear to primarily provide a disconnect of the breaker from the line and load bus bars. There are other connections to the breaker, however, which are commonly referred to as secondary or auxiliary connections, such as power to wind-up mechanisms, remote operator controls, wiring to meters from current transformers and the like.
A test position for the breaker is often provided whereby the line and load connections are broken, but the secondary connections are closed, allowing the breaker to be tested without actual engagement of the main bus bars. This test position usually requires that electrical wiring extend from the rear of the breaker, where an electrical connection with the bus bars is maintained, to the front of the breaker where tests or other operations are performed.
Although the insulation of the electrical wiring is adequate protection against incidental shorting, it is insufficient protection against other hazards. If the electrical wiring extends through the interior of the breaker, the moving parts of the interruption mechanism can damage the wiring. Another interior hazard is thermal damage from molten metal and hot plasma resulting from the arc generated by the interruption of the circuit. Electrical wiring routed on the exterior of the breaker housing is susceptible to damage from environmental hazards or field work performed on or near the breaker.
The need to protect a breaker's electrical wiring from these hazards is compounded by the increasing demand for breakers with improved performance in smaller housings. Decreasing the proximity of internal components with one another and with neighboring equipment increases the potential for harmful interaction therebetween. Furthermore, in view of increasing safety requirements for circuit breaker compartments already in operation that do not contain a protective apparatus for exposed electrical wiring connected to the breaker, there is a need for a field-installed protective wireway assembly that fits the circuit breaker housing designs of various manufacture.